The role of different parts of the spinal cord of cats in the coordination of the forelimbs and hindlimbs during overground stepping will be investigated. The involvement of specific fiber tracts will be analyzed by observing the patterns of interlimb coordination before and after careful placement of lower thoracic lesions to the particular parts of the cord. Interlimb coordination will be assessed using telemetered multichannel electromyography. The roles of lumbar interneurons in interlimb coordination will be analyzed using direct extracellular recordings during stepping. Chronically implanted fine wire electrodes will be used to relate patterns of interneuronal activity to the coordination of step cycles of the forelimbs and hindlimbs. The involvement of individual interneurons in normal interlimb coordination will be determined by a combined lesion-chronic extracellular recording technique. The results of this study are expected to provide evidence as to the nature of interactions between single limb locomotor pattern generators in the spinal cord which will be of use to motor control scientists and to clinicians attempting to manage motor control disorders. It is also expected to have significance for specialists in rehabilitation medicine dealing with patients with spinal cord injuries.